A MYSTERIOUS letter Z painted on Russian tanks and armoured cars could signify the "point of no return", experts say.
Several theories on the meaning of the symbol have been shared after Vladimir Putin's invasion force was filmed rolling towards Ukraine.
Footage showed tanks, self-propelled artillery, mobile rocket launchers and supply trucks on the move between six and 25 miles from the Ukraine border.
All were marked with similar symbols of a white Z inside a square box.
Read more World news
Military sources warned it showed the army was ready for a full-scale attack.
The symbols mirror UK and US tactics in the First Gulf War when forces sent to liberate Kuwait marked vehicles with an upturned chevron.
A source in Kyiv told The Sun at the weekend: “It would suggest final preparations are complete.
“It’s vital that any attacking force can be distinguished, particularly from the air where Russian forces will have complete control.
Most read in News
“The Ukrainians have very similar tanks and vehicles and will want to reduce the risk of friendly fire.”
Other sources added more clues to the meaning of the sinister Z markings.
Investigative journalist Aric Toler said his Bellingcat organisation had "been monitoring this stuff non-stop for eight years".
He said the group "has no idea what they are, and hasn't seen it before".
He agreed it spelled an invasion, adding: "So, assume the worst, I guess/fear."
Russia analyst Rob Lee has a different theory. He believes the symbols may refer to contingents of the invasion force assigned to Ukraine regions.
"It appears Russian forces near the border are painting markers, in this case 'Z,' on vehicles to identify different task forces or echelons," he said on Twitter.
🔵 Read our Russia - Ukraine live blog for the very latest updates
Others online suggested it stands for "Zorro squad" referring to the whole invasion force, or a secret name for a new unit.
Added to the mystery is the fact Z is a letter from the Roman alphabet and is not in the Cyrillic script used in Russia and Ukraine.
Former field intelligence officer David Kime said Z could stand for the name of Ukraine President Volodymyr Zelenskyy.
He claimed on Twitter he was told that by mercenaries from the Wagner Group, a brutal paramilitary organisation used by Putin for overseas black ops.
Kime added some military sources believe Z stands for "the point of no return".
The latest on the crisis in Ukraine...
- Donald Trump praised Putin's "genius" plan to invade Ukraine
- Foreign Secretary Liz Truss said Britain will "inflict pain" on Putin
- A trapped family spoke of their living hell in a blitzed corner of Ukraine
- Russia warned it won't stop at rebel enclaves, fuelling fears it will advance into territory held by Ukrainian forces
- Britain is to send more weapons to Ukraine as Boris Johnson said Putin was behaving in “an illogical and irrational frame of mind”
- Lord West, former chief of the Royal Navy, warned one wrong move could spark a nuclear war
The Z symbols were filmed two days before Putin ordered tanks and 10,000 troops into eastern Ukraine early on Tuesday.
Tanks spotted by a Reuters journalist rolling through one rebel-held town were not displaying any identifying marks.
Russia says the troops and heavy armour are on a "peacekeeping" mission after disputed claims the Russian-speaking population have come under attack.
Kyiv says Kremlin-backed rebels in the breakaway regions Luhansk and Donetsk blew up their own targets in "false flag" attacks as a pretext for Russia to invade.
Nato fears Russian tanks will not stop in the territory already held by rebels and will push on to occupy the whole of Ukraine.
Yesterday Putin raised alarm when he called for "demilitarisation" in Ukraine.
He also said he recognises the whole of Luhansk and Donetsk as independent nations, not just the parts under rebel control.
And his foreign minister questioned Ukraine's sovereignty in a blatant threat to the democratic country's existence.
Today Putin warned his "unparalleled" hypersonic missiles are ready for war.
His threat was delivered on Defender of the Fatherland Day, a national holiday honouring servicemen - and three days after he watched two of the new missiles tested from a Bond villain style “situation room”.
Read More on The Sun
Read more on The Sun
It comes amid reports Russia is stockpiling blood at field hospitals on the border.
Ukraine declared a state of emergency lasting 30 days and is calling up reservists aged 18 to 60 to take on the invading army.
We pay for your stories!
Do you have a story for The Sun news desk?
Email us at [email protected] or call 0207 782 4104. You can WhatsApp us on 07423 720 250. We pay for videos too. Click here to upload yours